The results of a simultaneous 13C and 15N labelling experiment with two different durum wheat cultivars, Blanqueta (a traditional wheat) and Sula (modern), are presented. Plants were grown from the seedling stage in three fully controllable plant growth chambers for one growing season and at three different CO2 levels (i.e. 260, 400 and 700 ppm). Short‐term isotopic labelling (ca. 3 days) was performed at the anthesis stage using 13CO2 supplied with the chamber air and 15NH4‐15NO3 applied with the nutrient solution, thereby making it possible to track the allocation and partitioning of 13C and 15N in the different plant organs. We found that photosynthesis was up‐regulated at pre‐industrial CO2 levels, whereas down‐regulation occurred under future CO2 conditions. 13C labelling revealed that at pre‐industrial CO2 carbon investment by plants was higher in shoots, whereas at future CO2 levels more C was invested in roots. Furthermore, the modern genotype invested more C in spikes than did the traditional genotype, which in turn invested more in non‐reproductive shoot tissue. 15N labelling revealed that the modern genotype was better adapted to assimilating N at higher CO2 levels, whereas the traditional genotype was able to assimilate N more efficiently at lower CO2 levels.
Iberian holm oak meadows are savannah-like ecosystems that result from traditional silvo-pastoral practices. However, such traditional uses are declining, driving changes in the typical tree—open grassland structure of these systems. Yet, there are no studies integrating the whole ecosystem—including the arboreal and the herbaceous layer—as drivers of greenhouse gas (GHG: CO2, CH4 and N2O) dynamics. Here, we aimed at integrating the influence of tree canopies and interactions among plant functional types (PFT: grasses, forbs, and legumes) of the herbaceous layer as GHG exchange drivers. For that purpose, we performed chamber-based GHG surveys in plots dominated by representative canopy types of Iberian holm oak meadows, including Quercus species and Pinus pinea stands, the last a common tree plantation replacing traditional stands, and unraveled GHG drivers through a diversity-interaction model approach. Our results show the tree–open grassland structure, especially drove CO2 and N2O fluxes, with higher emissions under the canopy than in the open grassland. Emissions under P. pinea canopies are higher than those under Quercus species. In addition, the inclusion of diversity and compositional terms of the herbaceous layer improve the explained variability, with legumes enhancing CO2 uptake and N2O emissions. Changes in the tree cover and tree species composition, in combination with changes in the structure and composition of the herbaceous layer, will imply deep changes in the GHG exchange of Iberian holm oak meadows. These results may provide some guidelines to perform better management strategies of this vast but vulnerable ecosystem.
The reference given here is cited in the text but is missing from the reference list -please make the list complete or remove the reference from the text: "University of Sheffield (2003)". Q1Please confirm that given names and surnames have been identified correctly. Q2The number of keywords provided exceeds the maximum (journal requirement: 3-5 keywords). Please delete extra keywords. Q3Ref. "University of Sheffield (2003)" is cited in the text but not provided in the reference list. Please provide it in the reference list or delete the citation from the text. Q4One or more sponsor names and the sponsor country identifier may have been edited to a standard format that enables better searching and identification of your article. Please check and correct if necessary. Q5Please provide the volume number and page range for the bibliography in Ref. "Bloom et al. (2014)". Q6Please provide complete details for Ref. "NOAA-ESRL (2014)". Q7 Table S4 is cited in the text but the corresponding input is not provided. Please provide it or delete these citations from the text. Q8Please specify the significance of footnote "*, ** and ***" cited in the Jouzel et al., 1993; Cowling and Sage, 1998). SinceAbbreviations: Amax, light and CO2-saturated net assimilation rate; Asat, lightsaturated net assimilation rate; cm, centimeter; Fv/Fm, maximum quantum yield of PSII; F v /F m , efficiency of the capture of excitation energy by open PSII reaction centers; gs, stomatal conductance; HI, Harvest Index; ITE, instantaneous transpiration of efficiency; Jmax, rate of photosynthetic electron transport; NsS, number of spikelets per spike; PSII, Photosystem II;˚PSII, relative quantum yield of PSII; qp, photochemical quenching; qN, non-photochemical quenching coefficient; NPQ, nonphotoquemical quenching; L, leaf; R, root; Rn, dark respiration; S, spike; SL, spike length; SN, spike number; St, stem; StL, stem length; StN, stem number; TFA, total flag area; TLA, total leaf area; TSA, total spike area; TStA, total stem area; Vc, max, maximum carboxylation velocity of Rubisco.* Corresponding author. (Aranjuelo et al., 2009a(Aranjuelo et al., ,b, 2011aPardo et al., 2009 with the continued emission of CO 2 will bring about changes in 106 land suitability and crop yields (IPCC, 2008(IPCC, , 2013. In particular, 107 these negative impacts are predicted to be greater for wheat than 108 for any other crop (IFPRI, 2008(IFPRI, , 2013. 109As was pointed out before, improvement of the quality of the is not yet well understood (Schnyder, 1993
Running title: Two distinct respiratory physiotypes in plants 2 SUMMARYThe origin of the carbon atoms in CO 2 respired by leaves in the dark of several plant species has been studied using 13 C/ 12 C stable isotopes. This study was conducted using an open gas exchange system for isotope labeling that was coupled to an elemental analyser and further linked to an isotope ratio mass spectrometer (EA-IRMS) or coupled to a gas chromatography-combustion-isotope ratio mass spectrometer (GC-C-IRMS).We demonstrate here that the carbon, which is recently assimilated during photosynthesis, accounts for nearly ca. 50% of the carbon in the CO 2 lost through dark respiration after illumination in fast-growing and cultivated plants and trees and, accounts for only ca. 10% in slow-growing plants. Moreover, our study shows that fastgrowing plants, which had the largest percentages of newly fixed carbon of leaf-respired CO 2 , were also those with the largest shoot/root ratios, whereas slow-growing plants showed the lowest shoot/root values.
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